Hello,
Use 4 ASA 5516-X with FirePOWER Services.
FirePOWER Services Software version 6.2.3.1 (The same trouble with version 6.2.3, and 6.2.2.2)
From time to time captive portal stop answering. User redirected to authentication page but page not accessible. Sfr module reboot resolve trouble on short time.
It happens by accident. Several times a day and maybe a week to work.
Need help.